Updated from 12:46 p.m. EST

Integrated oil giant

BP

(BP) - Get Report

reported that it lost more than $3 billion in the fourth quarter of 2008, down from an $8 billion gain in the prior quarter and a $4.4 billion gain in the year-ago period.

It was the company's first quarterly loss in more than seven years.

BP said in a press release that its net loss in the quarter was $3.34 billion. According to

Bloomberg

, the loss was equivalent to 18 cents per share, missing analyst estimates.

For the year, BP's profit was $21.16 billion, up from $20.85 billion in 2007.

BP's quarterly loss was attributable to a regulatory rule that requires oil companies to account for adjustments in the market value of their unsold inventories. Because the market price for crude oil and natural gas fell severely during the quarter, the value of the oil and gas in BP's storage tanks plummeted.

Without the mark-to-market adjustments, BP's replacement-cost profit last quarter was $2.59 billion, down 24% from its $3.40 billion replacement cost profit a year ago, and down 74% from $10.03 billion BP earned in the third quarter. Analysts were expecting quarterly replacement cost earnings of $3 billion, according to a Bloomberg survey.

Energy analysts tend to monitor replacement cost profits to measure operating proficiency.

BP said that its oil and gas production during the quarter was 3.95 billion barrels of oil equivalent per day, a 1% increase from the prior year. BP's average daily production increased 4% from the prior year if adjustments in BP's partnership agreements are taken into account.

The reactivation of BP's huge Thunder Horse program in the Gulf of Mexico was a major contributor to BP's higher production rate. Thunder Horse incurred severe damage from Hurricane Katrina in 2005, requiring lengthy repairs.

This earnings season has given investors a mixed bag of results from the integrated energy space. Like BP,

ConocoPhillips

(COP) - Get Report

missed analyst estimates for the quarter via a $31.8 billion net loss.

Exxon Mobil

(XOM) - Get Report

beat analyst estimates with quarterly earnings of $7.8 billion and record high earnings of $45.2 billion for the year.

Chevron

(CVX) - Get Report

also cleared analyst forecasts for the fourth quarter, reporting $4.9 billion in net income.

BP shares were recently up 1.7% to $42.29.